Variation in the intracellular polypeptide profiles from different isolates of bovine virus diarrhoea virus

Impact of bovine viral diarrhea virus on reproductive performance in cattle

The major economic impact of BVDV infections is in producing reproductive dysfunctions. The virus can have a detrimental impact on the developing fetus at all stages, but the most severe consequences occur early in gestation. The virus is maintained in the bovine population through the production of PI offspring. Only the NCB biotype of the virus can produce PI calves. The NCB biotypes is the one that produces the vast majority of BVDV infections and, as a consequence, the greatest economic losses. Biotype and antigenic variation are two independent variables and vaccines should emphasise antigenic composition, not biotype. A BVDV control program that does not emphasize heifers is doomed to failure.

Pathogenesis of mucosal disease: a cytopathogenic pestivirus generated by an internal deletion

Cytopathogenic bovine viral diarrhea virus (BVDV) arises by RNA recombination in animals persistently infected with noncytopathogenic BVDV. Such animals develop fatal mucosal disease. In this report, the genome of a cytopathogenic BVDV isolate, termed CP9, is characterized. CP9-infected cells contained not only viral genomic RNA of 12.3 kb but also a BVDV-specific RNA of 8 kb. cDNA cloning and sequencing revealed that the 8-kb RNA is a BVDV genome with an internal deletion of 4.3 kb. The 8-kb RNA represents the genome of a typical defective interfering particle (DI), since its replication was strictly dependent on the presence of a helper virus and strongly interfered with the replication of the helper. Cell culture experiments demonstrated that the CP9 virus stock contains two viruses, namely, a helper virus and DI9. While the helper virus alone was noncytopathogenic, the presence of the DI conferred cytopathogenicity. Expression experiments demonstrated that p80, the marker protein of cytopathogenic BVDV, is translated from the defective genome. The occurrence of this cytopathogenic DI is linked to a fatal disease in cattle.

Cloning, sequencing, and in vitro expression of glycoprotein gp48 of a noncytopathogenic strain of bovine viral diarrhea virus

Total cellular and viral RNA isolated from cells infected with noncytopathic bovine viral diarrhea virus (BVDV) strain 2724 was used for reverse transcription of viral specific sequences encoding the putative signal sequence and protein-encoding region of gp48. The cDNA template was amplified twice by the polymerase chain reaction with a nested set of primers designed from nucleotide sequences of cytopathic BVDV strains NADL and 72, and ligated into a plasmid vector. Nucleotide sequence analysis of the cloned cDNA indicated it was 921 base pairs long, encoded 307 amino acid residues, had high sequence homology to other pestiviruses, and had no significant homology to members of the Flaviviridae. In vitro expression of the cDNA yielded a 30 kDa protein that was precipitated by BVDV polyclonal antiserum. The protein was glycosylated in the presence of canine microsomal membranes to give a 46 kDa product and was secreted into the lumen of the microsomal vesicles. The characteristics of the putative signal peptide were consistent with signal sequences for protein translocation found in eukaryotes. A putative signal peptidase cleavage site was identified at a glycine residue at amino acid position 270. Based on signal peptidase cleavage of gp 48 and lack of a membrane anchor, we proposed that gp48 is a glycosylated protein lacking a transmembrane domain, and is analogous to the glycosylated secreted portion of the pre-M protein of flaviviruses.

Immunogens of bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is a ubiquitous pathogen of cattle that induces economically important diseases affecting multiple organ systems. In the United States, over 150 biological products are licensed for control of BVDV. These products contain live or killed BVDV, and many products contain other viruses or bacteria. Potency tests for these vaccines are based on animal inoculation and serology. For live virus vaccines, titration of viral infectivity in cell culture is an accepted alternative to animal inoculation. The immunogens in a killed virus vaccine may be measured by enzyme linked immunoabsorbent assay. Immunogens of BVDV that stimulate a protective immune response have not been conclusively identified. Epitopes on a putative viral envelope glycoprotein, gp53, are involved in viral neutralization. Other viral glycoproteins, gp48 and gp25, are immunogenic but epitopes on these proteins do not stimulate production of antibodies that efficiently neutralize virus. Progress in developing meaningful in vitro assays for quantitation of BVDV immunogens awaits identification of viral proteins that stimulate a protective immunity.

Anti-bovine viral diarrhoea virus antibodies in adult Zambian patients infected with the human immunodeficiency virus

Bovine viral diarrhoea (BVD) virus is a cosmopolitan pestivirus of animals which is associated with diarrhoea, immunosuppression and synergy with other pathogens. This study was conducted to establish the prevalence of anti-BVD virus antibodies in healthy Zambian adults and those with asymptomatic and symptomatic HIV disease. Sera from 1159 adults were tested for anti-BVD virus antibodies using the indirect immunofluorescence test and the confirmatory Western blot. Of the 1159 sera examined, 180 (15.5%) showed significantly elevated titres of anti-BVD antibodies. These included 70 out of 477 (14.7%) HIV-negative healthy adults; 73 out of 480 (15.2%) of HIV-positive asymptomatic individuals; 23 out of 129 (17.8%) HIV-seropositive patients with associated illnesses excluding diarrhoea; and 14 out of 73 (19.2%) of HIV-seropositive patients with chronic diarrhoea. HIV-seropositive patients with chronic diarrhoea or associated illnesses appear to have significantly increased seroprevalence of anti-BVD virus antibodies (P = > 0.01). The mechanism of interaction between BVD virus and HIV infections and the synergistic effects with other opportunistic pathogens in humans requires definition.

Distribution of cytopathogenic and noncytopathogenic bovine virus diarrhea virus in tissues from a calf with experimentally induced mucosal disease using antigenic and genetic markers

A comparative analysis of the distribution of cytopathogenic (cp) and noncytopathogenic (ncp) bovine virus diarrhea disease (BVD) virus in tissues from a calf with experimentally induced mucosal disease was performed using immunohistology and polymerase chain reaction after reverse transcription (RT-PCR) of viral RNA. For immunohistology, an antigenic marker on the superinfecting cp BVD virus defined by a monoclonal antibody (mab) was used, and overall presence of antigen was assessed with a pestivirus specific mab. The primers selected for RT-PCR detected the genomic insertion in the p125 region of the superinfecting cp BVD virus. Both methods gave consistent results.

Molecular characterization of positive-strand RNA viruses: pestiviruses and the porcine reproductive and respiratory syndrome virus (PRRSV)

Molecular characterization has become an important tool for the analysis of viruses including their classification. The manuscript focuses on the molecular analysis of two members of the genus pestivirus (hog cholera virus, HCV and bovine viral diarrhea virus, BVDV) and of the recently discovered porcine reproductive and respiratory syndrome virus (PRRSV). The first protein encoded within the single large pestivirus ORF is a nonstructural protein with autoproteolytic activity. The cleavage site between the protease and the capsid protein p14 has been predicted previously, but recent experimental data indicate that processing occurs at a different site. The capsid protein is followed by a putative internal signal sequence and three glycoproteins which are part of the virion envelope. According to a new proposal for the nomenclature of the structural proteins of pestiviruses they are termed C, E0, E1 and E2. The genomes of BVDV pairs isolated from animals which came down with mucosal disease were analyzed. The genomes from cytopathogenic (cp) BVD viruses may contain insertions highly homologous to cellular sequences. In addition, cp BVDV may differ from its non cytopathogenic (noncp) counterpart by mere rearrangement of viral sequences. The disease PRRS, which emerged a few years ago, is caused by a single strand RNA virus; the viral genome is of positive polarity and has a size of 15 kb. Data concerning morphology, morphogenesis and virion composition suggested already that PRRSV belongs to a group of so-called arteriviruses which comprises equine arteritis virus (EAV), lactate dehydrogenase elevating virus (LDV) and simian hemorrhagic fever virus (SHFV). This conclusion has now been confirmed by analysis of genome organization, gene expression strategy and by comparison of deduced protein sequences.

Rearrangement of viral sequences in cytopathogenic pestiviruses

Two cytopathogenic isolates of bovine viral diarrhea virus (cpBVDV) have been analyzed. For both viruses two regions of their genomic RNAs were found to be duplicated and rearranged. The viral genomes contain a small duplicated element (SD) derived from the genomic 5' end far downstream of its original context. This sequence is followed by a larger duplication which encompasses the region coding for the protein p80(LD), a molecular marker for cpBVDV. The SD element codes for the viral protease p20. In the case of the viruses analyzed here the aminoterminus of p80 is generated by autoproteolytic removal of the preceding SD-encoded protease. For one of the cpBVDV isolates a specific fusion protein (p28) could be identified which is composed of p20 and part of p10, another viral protein. Molecular characterization of the respective noncytopathogenic counterpart revealed that duplication and rearrangement of sequences as well as the expression of p28 and p80 are specific for the cytopathogenic virus.

The hog cholera virus

Hog cholera virus (HCV) is a spherical enveloped particle of about 40-60 nm dia. The viral genome is a single strand RNA of about 12,000 bases with positive polarity. One single large open reading frame codes for presumably four structural, i.e. three glycoproteins and a core protein, and about three to five nonstructural proteins. The functional role is not yet fully clear for all viral proteins. HCV belongs to the pestivirus group and it is closely related to bovine viral diarrhoea and border disease viruses. The relationship extends to morphology, antigenicity, host spectrum and molecular properties. Pestiviruses hold generic status in the family Flaviviridae.

Genetic diversity and BVD virus

The various measures of genetic variation of BVD virus was reviewed with emphasis on the implications for future control of virus-induced disease and diagnosis. While experimental data does not support unique serotypes for BVDV, there is substantial antigenic variation among the isolates examined. This variation may permit fetal infections even in animals assumed to be well vaccinated. The genetic differences between cytopathic and noncytopathic strains of BVDV are expressed in infected cells by the production of a p80 protein by cytopathic strains. In addition, cellular gene inserts have been detected in cytopathic strains. Monoclonal antibodies have demonstrated a high degree of diversity with the pestivirus population. Grouping of BVDV isolates by monoclonal antibody analysis is suggestive at best. The use of nucleic acid probes as diagnostic reagents has been compromised by the nucleic acid sequence variation found in the BVDV isolates tested.

Analysis of the bovine viral diarrhea virus genome for possible cellular insertions

Mucosal disease is the most severe disease resulting from bovine viral diarrhea virus (BVDV) infection in cattle. Two biotypes of BVDV may be isolated from animals with mucosal disease: cytopathic (cp) and noncytopathic (ncp). These "pairs" of cp/ncp viruses are often closely related and it has been suggested that the cp virus arises from a ncp virus by insertion of cellular RNA in the p125 region of the BVDV genome. We have used four pairs of cp/ncp BVDV isolated from cattle with mucosal disease, to examine the genomic sequence of the region of the genome coding for the nonstructural protein p125 (processed to p54/p80 in cp viruses) by PCR analysis and sequencing. We did not detect any cellular gene insertions in any of the four ncp viruses; however, we found a large duplication of the p80 gene and a ubiquitin gene insertion in three of the four cp isolates. Our results suggest that cellular RNA insertions in the p125 region may contribute significantly to the cytopathogenicity of BVDV. However, this does not appear to be the only mechanism of cytopathogenicity as we did not detect any insertions or duplications in one of the cp viruses. Comparison of the DNA sequence in the p80 region revealed greater homology within the "pairs" than to NADL, which lend further support to the hypothesis that a cp virus is originated from a ncp virus.

A monoclonal ELISA for bovine viral diarrhoea pestivirus antigen detection in persistently infected cattle

Detection of cattle persistently infected with bovine viral diarrhoea virus (BVDV) is crucial to controlling mucosal disease. A sandwich enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies raised against the 48-kDa glycoprotein and the 120/80-kDa protein was developed for detecting antigens in leucocytes of 3 persistently BVDV-infected calves. The test is simple, sensitive and rapid. Moreover the same ELISA was able to recognise Belgian field isolates of BVDV. These results show that the test can be applied in the field.

Pestivirus bovine viral diarrhea virus polypeptides: identification of new precursor proteins and alternative cleavage pathways

The genome of pestivirus bovine viral diarrhea virus (BVDV) contains a single 11,964 nt long open reading frame (ORF) that is capable of encoding a 449 kDa putative polyprotein. Although previous studies have described many virus-coded polypeptides that are believed to arise by post- and/or co-translational proteolytic processing in infected cells, there are two separate regions in the ORF for which no polypeptide products could be identified. In the present study using site specific antisera, we identified two new large proteins of Mr 175 and 172 kDa which encompass two previously described smaller precursor proteins, p125 and p133, respectively. These two large precursor proteins together with two other previously described proteins p22 and gp118 (Mr approx. 84 kDa; unglycosylated) account for the predicted Mr of the putative 449 kDa polyprotein precursor. Furthermore, we discovered three additional polypeptides of Mr 168, 96 and 72 kDa encoded by the last third of the genome. These proteins may arise by an alternative cleavage pathway of the precursor protein p172. A modified and updated map of BVDV ORF incorporating the above findings is presented.

Viral cytopathogenicity correlated with integration of ubiquitin-coding sequences

The RNA genomes of cytopathogenic bovine viral diarrhea virus (BVDV) isolates contain insertions highly homologous to cellular sequences. For two of them the insert was identified as ubiquitin coding sequence. The genome of BVDV Osloss contains exactly one ubiquitin gene monomer. In the case of BVDV CP1 the cellular insertion comprises one complete ubiquitin gene and part of a second monomer. The host cell-derived element in the CP1 genome is embedded in a large duplication of about 2.4 kb of viral sequences. Cellular insertion and duplication were not found in the genome of NCP1, the noncytopathogenic counterpart of CP1. These results strongly suggest that recombination between viral and cellular RNA is responsible for development of the cytopathogenic viruses, which is linked to pathogenesis of a lethal disease in cattle.

Immunological reactivity of bovine viral diarrhea virus proteins after proteolytic treatment

The immunological reactivity of bovine viral diarrhea virus proteins after proteolytic treatment is described. The results indicate that the epitopes detected are very dependent on conformation of the protein. A partially protease resistant 22 kD fragment of the biotype-specific p80 is identified.

BVD monoclonal antibodies: relationship between viral protein specificity and viral strain specificity

Seventeen monoclonal antibodies raised against bovine viral diarrhoea virus were divided into three groups on the basis of radioimmunoprecipitation results. Seven monoclonal antibodies precipitated a polypeptide of 80kD and defined four domains, all of which showed considerable conservation amongst the 180 pestivirus strains and isolates examined. Nine monoclonal antibodies, including six with virus neutralizing activity, precipitated a 53kD polypeptide and all appeared to be directed towards a single domain of clustered epitopes. Several of these epitopes were present in many ruminant virus strains and isolates, but not in hog cholera viruses. A single monoclonal antibody precipitated a 48kD polypeptide, defining an epitope that was also present on many ruminant viruses, but not hog cholera viruses. Most pestiviruses from cattle and some from sheep shared a number of epitopes located on three different proteins.

Insertion of cellular sequences in the genome of bovine viral diarrhea virus

The genomic sequences of four pestiviruses, two BVDV strains (Osloss and NADL, both of which are cytopathogenic) and two HCV strains, were analyzed. Comparative studies revealed the presence of small insertions of cellular sequences in the genomes of both BVDV strains; the insertions are located in a region coding for a nonstructural protein. Such insertions are not present in the HCV sequences. The insertion identified in BVDV Osloss encodes a complete ubiquitin-like element. The sequence inserted in the BVDV NADL genome shows no homology to a ubiquitin gene but is almost identical with another bovine mRNA sequence. Molecular characterization of a BVDV "pair", isolated from an animal with mucosal disease, led to the detection of a ubiquitin-like sequence in the genome of the cytopathogenic strain, but not of the noncytopathogenic strain. It is proposed that recombination between viral and cellular RNA leads to formation of cpBVDV genomes. This hypothesis has direct implications for the pathogenesis of mucosal disease.

The pathways for bovine virus diarrhoea virus biotypes in the pathogenesis of disease

BVDV infections of cattle ranges from the transient acute infections, which may be inapparent or mild, to mucosal disease which is inevitably fatal. On occasions the acute infections can lead to clinical episodes of diarrhoea an agalactia but as these syndromes cannot be reproduced experimentally, the pathogenesis remains unclear. The immunosuppressive effect of acute BVDV infections can enhance the clinical disease of other pathogens and this may be an important part of the calf respiratory disease complex. Although BVDV antigen has been demonstrated within the lymphoid tissues, for prolonged periods, the evidence for viral latency remains to be proven. Venereal infection is shown to be important in the transfer of virus to the foetus and congenital infections can cause abortions, malformations and the development of persistently viraemic calves. The two biotypes of BVDV, non-cytopathogenic and cytopathogenic, are described. Their sequential role in the pathogenesis of mucosal disease arises from the initial foetal infection with the non-cytopathogenic virus and the subsequent production of persistently viraemic calves. These calves may later develop mucosal disease as a result of superinfection with a "homologous" cytopathogenic virus and the possible origin of this biotype by mutation is discussed. Chronic disease is defined as a progressive wasting and usually diarrhoeic condition; it is suggested that this may develop following superinfection of persistently viraemic cattle with a "heterologous" cytopathogenic biotype.

Molecular characterisation of the coding region for the p125 from homologous BVDV biotypes

We amplified and sequenced the p125 coding regions of a 'homologous' pair of BVDV biotypes, Pe515 cytopathogenic and non-cytopathogenic. The sequences were aligned with the published sequences of Osloss, NADL and the HCV Alfort strains, but no insertions of host sequence were observed in that region.

Viral protein production in homogeneous and mixed infections of cytopathic and noncytopathic BVD virus

Experiments were conducted to examine dual infection of cultured cells with cytopathic and noncytopathic bovine viral diarrhea virus (BVDV). Cell monolayers infected with a noncytopathic BVDV isolate and subsequently superinfected with a cytopathic BVDV isolate were refractive to the cytopathic effects of the cytopathic BVDV isolate, as reported in the literature. Immunofluorescence staining of superinfected cultures with monoclonal antibodies specific for the cytopathic or the noncytopathic viral isolate, demonstrated that cells in superinfected cultures contained both viral biotypes. Immunoprecipitation was used to compare the temporal detection of viral induced polypeptides in superinfected cultures to that of cultures infected with a single viral biotype. In single cytopathic viral infections, viral induced polypeptides of 80 kDa and 53-56 kDa are detected simultaneously, but in superinfections a 4 h gap occurred between detection of the 53-56 kDa polypeptide and detection of the 80 kDa polypeptide.

Antigenic variations in bovine viral diarrhea viruses detected by monoclonal antibodies

Five murine monoclonal antibodies (MAbs) against the NADL strain of bovine viral diarrhea (BVD) virus were developed, identified, and characterized. Four of the MAbs were directed against a 53-kilodalton (kDa) viral protein, and one was specific to a 47-kDa polypeptide. Competitive radioimmunoassay showed that two MAbs were specific to related epitopes of the 53-kDa protein, and the other three MAbs were each specific to a different epitope. The MAbs were used to study heterogeneity among BVD virus strains. Various degrees of reactivity of cytopathic and noncytopathic virus isolates were detected by virus neutralization and immunofluorescence assays. The virus isolates were divided into six groups based on the neutralization test. The results indicated that the 53-kDa glycoprotein of BVD virus is the major protein involved in virus neutralization and that only a few epitopes of the protein contribute to the neutralization. None of the MAbs neutralized all the BVD virus isolates tested in this study, suggesting antigenic variations among BVD virus isolates.

Molecular cloning and nucleotide sequence of hog cholera virus strain Brescia and mapping of the genomic region encoding envelope protein E1

Genomic RNA of hog cholera virus (HCV) strain Brescia was cloned and sequenced. The nucleotide sequence was deduced from overlapping cDNA clones and comprises 12,283 nucleotides. We cloned the complete 3' end of the HCV genome, but could not unequivocally prove that the cDNA sequence also completely covers HCV RNA at the 5' end. The HCV genome contained one large open reading frame, which spans the viral plus strand RNA and encodes an amino acid sequence of 3898 residues with a calculated molecular weight of 438,300. To identify structural HCV glycoproteins, we prepared rabbit antisera against three synthetic peptides deduced from the sequence. Because one of these antisera reacted with a 51- to 54-kDa glycoprotein (envelope protein E1 of HCV) on Western blot, the genomic position of the sequence encoding gp51-54 could be clearly established. The amino acid sequence of Brescia was compared with that of HCV strain Alfort and that of BVDV strains NADL and Osloss. The degree of homology between the two HCV strains was 93%, and between Brescia and the BVDV strains about 70%. NADL contained an inserted sequence of 90 amino acids that was absent from the sequences of Brescia, Alfort, and Osloss, whereas Osloss contained an inserted sequence of 76 amino acids that was absent from the sequences of Brescia, Alfort, and NADL. Sequences in p80, the most homologous protein among pestiviruses, showed similarity to six sequence motifs found conserved in helicase-like proteins represented by eIF-4A. Furthermore, a trypsin-like serine protease domain detected in p80 of BVDV was also found conserved in HCV, suggesting that pestivirus p80 may be bifunctional.

Pathogenesis of mucosal disease and molecular aspects of bovine virus diarrhoea virus

Studies carried out over three decades, on the pathogenesis and epidemiology of bovine virus diarrhoea virus (BVDV), have provided the basis for our understanding of the aetiology of mucosal disease. Experimental reproduction of the disease has demonstrated the mechanism of sequential infection and the role of the two virus biotypes. The need for "homogeneity" between the biotypes, causing mucosal disease, has demonstrated the precision of immunotolerance. The origin of the cytopathogenic biotype remains unclear but molecular studies may provide the solution. Recent findings have revealed the absence of an 80 kDa polypeptide in the non-cytopathogenic isolates. This protein is related to the 120 kDa polypeptide that is present in both biotypes. Genomic sequences for two isolates have been reported. An extensive homology to the protein ubiquitin has been identified only within the Osloss sequence in the region flanking coding sequences for the 80 kDa and 120 kDa proteins. Advances in the development of molecular gene probes and monoclonal antibodies will provide new tools for furthering our understanding of the pathogenesis, epidemiology and interrelationships of pestiviruses that infect pigs, cattle and sheep.

Pestiviruses: a review

Pestiviruses comprise a group of economically important animal pathogens, namely hog cholera, bovine viral diarrhoea and border disease viruses. The viruses are serologically closely related and share a common host spectrum, i.e. pigs and numerous domestic and wild living ruminants. Interspecies transmissions occur frequently. Despite some common features in their natural hosts, pathogenesis of pestivirus-induced disease is complex; especially some aspects of highly fatal mucosal disease of cattle are still enigmatic. Pestiviruses are amongst the smallest enveloped single-stranded RNA viruses with an icosaeder-shaped nucleocapsid. They are currently classified as Togaviridae. However, based on recent progress in the molecular characterisation of the viruses their taxonomic real-location seems inevitable. Viral RNAs studied so far display one large open reading frame and in infected cells no subgenomic RNA is demonstrable. Structural proteins are coded for by genes located at the 5' end of the RNA. The majority of the genome codes for 2-3 nonstructural proteins. Virions are composed of a major and one minor envelope glycoprotein with molecular weights of 53 and 48 kD respectively. The core is composed of a small protein with a molecular weight of 20 kD. Analysis of viral proteins with monoclonal antibodies has yielded detailed information about the antigenic composition of both structural and nonstructural proteins.

Intracellular virus-induced polypeptides of pestivirus border disease virus

Intracellular virus specific polypeptides of pestivirus, border disease virus (BDV) in bovine turbinate cells were analysed by radio-immunoprecipitation with specific antisera. Eleven viral polypeptides with molecular weights of 220, 165, 118, 84, 66, 58, 55, 53, 45, 37 and 31 kDa, respectively, were detected in infected cells. Of these, the 165, 118, 84, 66, 58, 55, 53, 45 and 31 kDa proteins were found to be glycosylated. Comparative studies indicated that the polypeptides induced by BDV share many antigenic epitopes with those of the polypeptides induced by bovine viral diarrhea virus (BVDV), a serologically related virus of the same genus, pestivirus. The polypeptide profile of BDV appeared to be more similar to that of the noncytopathic BVDV strain NY1 compared to that of cytopathic BVDV strains NADL and Singer. Peptide mapping analysis of homologous polypeptides from BVDV and BDV confirmed their structural relatedness.

An ELISA for detecting pestivirus antigen in the blood of sheep persistently infected with border disease virus

A monoclonal antibody capture enzyme-linked immunosorbent assay (ELISA) has been developed to detect a pestivirus-specific antigen in leucocytes of sheep persistently infected with border disease virus. A blind trial was conducted to compare the specificity of the ELISA with conventional tissue culture virus isolation on blood samples from 58 sheep, aged 3 to 48 months. There was total agreement between the two tests; 27 sheep were shown to be BDV-infected. The ELISA OD values of the positive samples ranged from 0.12 to 0.86 and were not related to age, strain of virus with which they were infected or presence of serum neutralising antibody. Negative samples had OD values between 0 and 0.02.

Effect of host cell on the in vitro characteristics expressed by two bovine viral diarrhea virus strains

Growth curves, immunofluorescence assays and radioimmunoprecipitation analysis of bovine viral diarrhea virus (BVDV)-specified polypeptides were used to determine the susceptibility of bovine endothelial cells (BECs) to infection with strains of BVDV. One strain of the virus, NY1, normally non-cytopathic when grown in bovine turbinate cells (BTUs), did not parallel this type behavior in BECs. Virus replication kinetics, morphological changes in infected cells and resolution of viral polypeptides suggest that NY1 replicated and showed cytopathologic changes in infected BECs similar to a cytopathic strain of BVDV, strain C24V. Two previously unreported viral polypeptides were identified in NY1-infected endothelial cells. These polypeptides had molecular weights of 92,000 (92kDa) and 72kDa. These findings suggest that BVDV-cell interactions occurring in BECs differ from those observed in similarly infected BTUs.

Severe thrombocytopenia in young calves experimentally infected with noncytopathic bovine viral diarrhea virus

Seven calves between 1 week and 2 months of age were infected with a noncytopathic field isolate of bovine viral diarrhea virus (BDV) in order to evaluate the effect of BDV infection on the concentration of circulating platelets in the blood. All calves were determined to be free of BDV and neutralizing antibodies to BDV before infection. Platelet counts were performed on a daily basis over a 30-day period beginning at the time of infection. By 2 weeks postinfection, all calves showed a significant drop in the number of circulating platelets and a marked hyperplasia of megakaryocytes in the bone marrow. In three of the seven calves, thrombocytopenia was severe (less than or equal to 5,000/microliters) for 1 to 6 days. In two of these three animals, extensive petechial and ecchymotic hemorrhages were observed on all mucosal surfaces and on various internal organs during the period of severe thrombocytopenia. BDV was consistently isolated from the platelets during the early phases of the infection, and viral antigen was occasionally detected on platelets by a fluorescent-antibody assay. The results demonstrate that BDV infection is associated with decreases in platelet numbers and suggest that platelets may serve as carriers of circulating virus.

The application of monoclonal antibody panels to characterize pestivirus isolates from ruminants in Great Britain

Monoclonal antibodies were prepared against bovine virus diarrhoea virus and hog cholera virus. They were used to test 101 field isolates of ruminant pestivirus in a simple binding assay using an indirect immunoperoxidase label on fixed cell cultures. The monoclonals were divided into three panels: (1) pestivirus group specific, (2) hog cholera specific, (3) selectively reactive with ruminant pestiviruses. The reaction patterns with panel 3 were analyzed by a computer spreadsheet to determine the percentage match with seven reference patterns. Field viruses could be divided into two main groups. Group A consisted of 73 (87%) of the 84 bovine isolates and three (19%) of the 16 ovine, and was reactive with 40% or more of panel 3. Group B showed only limited reactivity with panel 3 and comprised 13/16 (81%) of the ovine (border disease) isolates together with the remaining 11 (13%) bovine viruses.

Two monoclonal antibodies (CC17, CC29) recognizing an antigen (Bo5) on bovine T lymphocytes, analogous to human CD5

Two new monoclonal antibodies (CC17 and CC29) raised against bovine thymocytes are described. The antibodies, both of which were IgG1, recognize a molecule of approximately 67,000 molecular weight on bovine T cells. They react T cells in peripheral blood, the lymph node paracortex and the periateriolar lymphoid sheath in the spleen. Both the cortex and medulla of the thymus are stained but the medulla reacts more intensely. They do not stain B cells in peripheral blood, the ileal Peyer's patch, the cortex or the primary follicles in lymph nodes. No activity was found on cells outside the lymphoid system, i.e. monocytes, alveolar macrophages or endothelial and epithelial tissue. The antigen recognized is considered to be the bovine homologue of CD5 (T1) in humans and Lyt1 in mice. The mAbs appear to be particularly useful for detecting cells in the peripheral blood of young calves which are of the T cell lineage but do not express BoT2 or the mature pan T cell antigen recognized by mAb IL-A27 and may thus allow identification of a population of bovine lymphocytes previously described as null cells.

Molecular cloning and nucleotide sequence of the pestivirus bovine viral diarrhea virus

The RNA genome of the cytopathic NADL isolate of bovine viral diarrhea virus (BVDV) has been molecularly cloned and the nucleotide sequence determined. The cloned sequence was 12,573 nucleotides in length, corresponding to a molecular weight of 4.3 X 10(6), having a base composition of 32.2% A, 25.7% G, 22.1% U, and 20.0% C. However, the sequences at the 5' and 3' termini of the RNA have not been unequivocally established. A single major open reading frame extending the length of the molecule was found in the viral-sense (positive polarity) sequence. This open reading frame was capable of encoding 3988 amino acids, representing 449 kDa of protein.

Proteins encoded by bovine viral diarrhea virus: the genomic organization of a pestivirus

The genome of bovine viral diarrhea virus (BVDV) contains a single large open reading frame capable of encoding 449 kDa of protein. Short segments from along the length of the molecularly cloned BVDV genome were engineered so as to be expressed as bacterial fusion polypeptides in Escherichia coli. These BVDV analog fusion proteins were used as immunogens to generate a panel of sequence-specific antisera. These antiserum reagents were in turn employed in immunoprecipitation analyses to identify the authentic BVDV protein to which they were directed. The results allowed for the identification and positioning along the genome of BVDV gene products accounting for approximately 83% of the coding capacity of the virus. A preliminary map of the genetic organization of BVDV is presented and discussed.

Bovine viral diarrhea virus proteins: heterogeneity of cytopathogenic and non-cytopathogenic strains and evidence of a 53K glycoprotein neutralization epitope

Intracellular virus-induced polypeptides from 3 cytopathogenic and 2 non-cytopathogenic bovine viral diarrhea (BVD) virus reference strains were analyzed by radioimmunoprecipitation and polyacrylamide gel electrophoresis, using a specific bovine multivalent antiserum and a neutralizing BVD-virus monoclonal antibody. Electrophoretic patterns of major proteins demonstrate extensive variation between strains. Most notably, a major 80,000 (80K) polypeptide was present in all cytopathogenic strains but absent in both non-cytopathogenic strains. Furthermore, a neutralizing monoclonal antibody produced against the NADL strain immunoprecipitated a 53K glycoprotein indicating that this protein carries an important neutralization epitope that is not present in all strains tested.